It is common practice to store or package surface-mount electronic components in evenly-spaced pockets on linear tape. For convenient storage, transport, and dispensing of these components, linear tape containing the components is typically wrapped around round reels. Within the electronics industry, this practice is referred to as “tape and reel” packaging. In this way a large number of small components may be stored in an orderly way for use in automated robotic assembly machines. The linear tape is typically provided with small, equally-spaced holes along the length of the tape, which facilitate feeding the tape into automatic machines, which typically include cogged wheels that engage the holes in the tape.
There are several conventional methods for measuring the number of parts left on a reel after an unknown quantity of parts have been removed. A first method involves estimating the number of parts by comparing an outside diameter of the last wrap of tape to a graduated scale printed on the reel frame. A second method involves running the entire tape through a counting machine to count every part. A third method involves weighing the reel to estimate part counts. There are several drawbacks to all of the aforementioned conventional practices.
The first conventional method results in only a rough estimate, the accuracy of which is limited by the markings on the reel. Such markings are often only accurate to within 25% of the actual quantity of parts. Further, variations in the thickness of the tape used contribute to this inaccuracy. Since there is no standard for tape thickness due to the wide variety of component sizes, in many cases the reel markings are not accurate for the tape that resides on the reel. Attempts to reduce the inaccuracies due to incorrect reel marking are further complicated by the inability to verify which tape thickness a reel is actually marked for.
The second conventional method of measuring part quantities involves mounting the reel to be counted on a spindle and feeding the tape through a counting mechanism and onto an empty reel. The empty reel is then rotated to pull the tape off of the primary reel and though the counting mechanism. When the counting is finished, if it is desired to have the tape back on the primary reel, it must then be transferred back to the primary reel in a similar manner. While this method is generally very accurate, since it counts each part, it is also a tedious and time-consuming process that requires a bench mounted machine and increases the cost of production. Furthermore, additional time is consumed transporting these reels to and from the counting machine. Further, there must be a matching blank reel available for the process to take place. This method also requires a fairly skilled operator to adjust the machine for different part types and reel sizes. Moreover, the cost of these counting machines is often prohibitive for small businesses.
The third conventional method of measuring part quantities, which involves weighing the reel to determine part counts, requires a very accurate weighing scale. Typically, this method requires knowledge of the weight of the reel when full and when empty. This accuracy needed for this method can typically only be obtained with a bench top scale that is properly leveled. Therefore, it is difficult to transport this type of system to different points of use. Further, determination of the empty weight of the reel may be hard to determine unless an empty reel of the exact type to be measured is also available. Highly accurate scales can be costly, and still require some means of calculating the number of parts once the weight has been determined.
It would therefore be desirable to have a portable apparatus which allows for component counts to be determined with a reasonably high degree of accuracy, and which is less expensive than some of the conventional measurement devices mentioned above. Further, it would also be desirable for the portable apparatus to be easily operated, eliminating the need for a skilled operator.
Embodiments of the invention provide such an apparatus. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.